Sump Pump - Drain the entire pit?

I just bought a house that has a sump pump in the finished basement. The water table must be pretty high, because the water level sits about 8 inches below my slab. I have a pump that sits below the water level.

I've been watching this thing operate over and over and something just doesn't seem right. It has a big rubber float that dangles up from the pump. When it switches, the pump sucks the water up and out, but turns off before draining the entire sump. Do these pumps have to stay completely submerged? I would like the entire pit to drain, so there is more room and therefore more time between cycles. How do I make the pump run longer when it switches on. Is it timed or what?

Thanks for any help you can offer.

You can usually cause it to pump down farther by changing the attachment point. If you lower the float attachment point you will lower the depth to which it pumps, and you will make it come on at a lower level.

If you lengthen the distance from the float to the attachment point you will increase the range between start and stop.

If you lengthen it a little and lower the attachment point a little you can lower the final water level and keep the same start level.

Now that you know how to do it, you should decide if you want to do it. If you pump farther below the water table, more water will flow into the sump. You can try it to see if you can pump down the water table.

You can test for increased flow by measuring the on-time fraction at the current level, and then check the on-time fraction after you lower the pumping level.

I'd ask myself how long the thing has been installed like this AND how it has worked in the past.

Then if it has been there a number of years, I would decide to be smart and not fix something that isn't broken.

And good luck trying to pump down the water table, that won't be happenin' anytime soon.

BTW, where does the discharge water go? If not far enough away form the foundation, you end up moving the same water over'n over'n over... a real waste of effort and money. So maybe there is another feel good project in all that somewhere....

Another one is a battery backup for the sump pump so it can work when needed like during a thunderstorm etc. when there's no power. Moving downspout water farther away from the house is another good one. Keeping rain gutters clean is good too. Having a spare sump pump identical to this one to make it very simple and fast to replace it would help too. They usually only quit when they should be running...

Thank you for your help!

I will stick my head down the sump again, but it looked like the connection point is fixed to the top of the pump. It looks like a metal horshoe with screws holding it to the pump. I would imagine I need to loosen the screws to lenthen and shorten the cable lenth. I'm not sure I can change the location though.

I know what you're saying about fixing something that isn't broken. Since I just moved in, I'm not sure how it has worked in the past. Based on other things I've discovered in the house, I'm not real confident the previous owners would have the sump set up the most efficient way.

The discharge pipe goes about 3 feet above the sump, does a 90 out the side of the house, then down into the ground and travels about 100 feet underground to the swamp in the backyard. I would assume the groundwater is at the level of the swamp, which is about 5 feet lower than my basement. That's why I don't understand why the sump sits wet all the time. There must be some sort of seam or spring in the hill (I have a walk-out).

I just bought a battery backup and started to install it yesterday. That's how this all started. I sat there watching this thing work trying to figure out what was going on before I started adding the second pump.

Can these submersible pumps sit dry until they are needed, or do they have to stay wet?

I'm no pumpologist, but you should be okay pumping the sump dry as long as you have a weep hole drilled in your discharge pipe. This will allow water to enter the pump and prime it so it doesn't air lock when it is needed. If anyone sees anything wrong with my explanation, please correct me. I don't want to be indirectly responsible for ruining a basement